In recent years, flat panel displays represented by electronic books and liquid crystal displays are more and more popular. Most electronic books and liquid crystal displays are of the type of active matrix, which have a TFT array substrate. Generally, in the design of the TFT array substrate for the electronic paper and the liquid crystal display, the aperture ratio of pixels is expected as high as possible. FIG. 1 is a schematic partial plan view of a TFT array substrate with higher aperture ratio in the prior art, and FIG. 2 is a schematic sectional view of the TFT array substrate taken along the line a-a in FIG. 1. Referring to FIG. 1 and FIG. 2, the TFT array substrate in the prior art includes TFT switches and a common electrode 17 which are formed on a glass substrate 10. For the case in the prior art as shown in FIG. 1, the TFT switch is a dual-TFT switch, including a first TFT switch 11 and a second TFT switch 12. The first TFT switch 11 includes a first gate electrode 111, a first source electrode 112 and a first drain electrode 113 which are disposed at both sides of the first gate electrode 111 respectively. The second TFT switch 12 includes a second gate electrode 121, a second source electrode 122 and a second drain electrode 123 which are disposed at both sides of the second gate electrode 121 respectively, and the second drain electrode 123 also extends in a pixel region. The first gate electrode 111 and the second gate electrode 121 are both electrically connected to a scan line 15, the first drain electrode 113 is electrically connected to the second source electrode 122, the second drain electrode 123 is electrically connected to a pixel electrode 18, and the second drain electrode 123 is disposed in the pixel region. The TFT array substrate in the prior art further includes a passivation layer 14 covering an array of the TFT switches, an organic material layer 20 covering the passivation layer 14, a via hole 21 disposed in the organic material layer 20 and the passivation layer 14, and the pixel electrode 18 covering the organic material layer 20 and the sidewall and bottom of the via hole 21. Referring to FIG. 1 and FIG. 2, the pixel electrode 18 has an overlapping portion overlapped by the adjacent data line 16 and the adjacent scan line 15. The thick organic material layer 20 with low dielectric constant being disposed between the pixel electrode 18 and the data line 16 overlapped by the pixel electrode 18, between the pixel electrode 18 and the scan line 15 overlapped by the pixel electrode 18, the parasitic capacitance between the pixel electrode 18 and the data line 16 overlapped by the pixel electrode 18, between the pixel electrode 18 and the scan line 15 overlapped by the pixel electrode 18 may be reduced. In this way, not only the aperture ratio of the pixel structure may be improved, but also capacitive crosstalk may be reduced.
In the prior art, a method of forming the TFT array substrate includes: providing the glass substrate 10, and forming TFT switches, scan lines, data lines and a common electrode layer on the glass substrate 10; then forming a passivation layer, and etching the passivation layer to form a first via hole for exposing the second drain electrode 123 of the TFT switch; next, forming the organic material layer 20, and forming a second via hole in the organic material layer 20, the second via hole being connected with the first via hole to form the via hole 21; and then, forming a pixel electrode layer, and patterning the pixel electrode layer to form the pixel electrode 18, the pixel electrode 18 being electrically connected to the second drain electrode 123 through the via hole 21. However, the low K organic material used is expensive and the manufacturing process is complex. Therefore, the yield for manufacturing the existing TFT switch array base plates is decreased and the cost is high.